Method and apparatus for tracing a track



June 17, 1969 H. FRENK 3,450,934

METHOD AND APPARATUS FOR TRACING A TRACK Filed June 7, 1967 Sheet I of 5 displacement (i/(Mg INVENTOR BY HELMUTH FRENK A'fTORNEYS June 17, 1969 H. FRENK 3,450,934

METHOD AND APPARATUS FOR TRACING A TRACK Filed June 7, 1967 Sheet 2 of 5 Fig. 3

llllllllllll INVENTDR HELMUTH FRENK ATTORNEYS Sheet H. FRENK METHOD AND APPARATUS FOR TRACING A TRACK June 17, 1969 Filed June 7, 1967 INVENTOR HELMUTH FRENK ATTORNEYS June 17, 1969 H. FRENK 3,450,934

METHOD AND APPARATUS FOR TRACING A TRACK Filed June 7, 1967 Sheet 4 of 5 Fig. 8

/0/ I02 I03 I04 /05 F-- 1 6 5% f I I J 2/6 2/2 3 20 21a M- INVENTDH HELMUTH FRENK b mm ATTORNEYS June 17, 1969 H. FRENK 50,

METHOD AND APPARATUS FOR TRACING A TRACK INVENTUR Br HELMUTH FRc/vK W 19 'Zl/LZQ ATTORNEYS United States Patent US. Cl. 315- 11 Claims ABSTRACT OF THE DISCLOSURE A new method for tracing a track by means of the flying spot of a cathode ray tube (hereinafter termed CRT) is outlined which method comprises the steps of generating an oblong pattern by means of a rotating flying spot; tilting the flying spot pattern in order to adjust the main axis to a direction parallel to the tangent to the track to be traced; shifting the flying spot pattern in order to bring the central point of said main axis into contact with said track to be traced and displacing said flying spot pattern in such a way as to move the central point along the track to be traced.

Thus it is not the flying spot itself that is used for tracing the track, but rather it is the central point of the flying spot pattern which serves this purpose.

A photoelectric receiver is employed for generating control signals for the tilting and the movement of the flying spot pattern. Additionally, a particular field of application of this new method is outlined in the disclosure: the method is used for tracing nuclear tracks on stereoscopic bubble chamber track photographs.

BACKGROUND OF THE INVENTION F ield of the invention My present invention relates to the technique of analysing the properties of a single line or track or a pattern of lines or tracks. More specifically, my invention relates to the determination of the angle of inclination and/or the curvature of said tracks by defining as many of their coordinates as possible by means of the flying spot of a CRT.

Description of the prior art There are already devices known to those skilled in the art, which make use of mechanical means, e.g. servomotors or pivotable mirrors in order to trace a track with a spot of light. A photoelectric receiver is employed for detecting any deviation of the spot from the track to be traced. Should this occur, the output signals of the photoelectric receivers will generate control signals for correcting the adjustment of the mechanical means whereby the light spot will be brought back onto the track. It is a disadvantage of these devices, however, that-caused by the inertia of said mechanical means-their action is only very slow.

This disadvantage can be readily avoided by using a spot of light which is capable of being displaced very rapidly. A spot of this nature is, for example, the flying spot of a CRT. Deviations of this flying spot from the track to be traced have, of course, also to be corrected immediately. Owing to the speed with which the flying spot moves or oscillates, extremely voluminous and costly devices are required to this end, e.g. expensive computers.

The main object of the invention is therefore to provide a new tracing method and apparatus which, at least, produces the same result as is obtained from the known methods, which new method, however, requires less expensive and voluminous elements.

3,450,934 Patented June 17, 1969 SUMMARY OF THE INVENTION The new method as outlined in the abstract of the dis closure is performed according to the invention by conmeeting at least six control voltages in pairs to the CRT. The flying spot is thereby caused to move along an oblong pattern which is approximately of double the width and .n length of approximately ten times the width of the track to be traced. The crossing of the track by the flying spot generates output signals with the photoelectric receiver. Said signals are related to the four quadrants of the flying spot pattern and by comparing said signals by means of phase sensitive rectifiers control signals are obtained for the inclination of the main axis of the flying spot pattern and for the location of its central point. Said signals are made use of to bring said central point in tangent relationship with the track to be traced.

By rectification and subsequent integration, signals are produced for controlling the motion of the flying spot pattern in the direction of its main axis. From said signals information is obtained regarding the location and the shape of the track to be traced.

For spotting the track to be traced in a whole pattern of tracks or lines a scanning motion of the flying spot is produced. When the flying spot crosses the track to be traced the scanning motion is stopped and the track will be traced according to the method outlined above. The path of the flying spot may be stored by a storing television camera tube, e.g. a Vidicon.

From the control voltages and/or control currents and from the signals generated by the photoelectric receiver information is derived about possible branches in the track to be traced or about its end. After reaching this end the scanning motion will again be resumed. It will start from the first point of coincidence, ice. from where the previous scanning motion crossed the first track. Means are provided, however, which prevent a stopping of the scanning motion if the flying spot again crosses a track which has already been traced and which therefore is already stored on the screen of the Vidicon.

DESCRIPTION OF THE DRAWINGS FIGURE 1 shows schematically a track to be traced together with a flying spot pattern;

FIGURES 2a-2d show schematically four diflerent flying spot patterns as may be produced by connecting different pairs of control voltages to the CRT;

FIGURE 22 is a block diagram of signals as received after coincidence of the control point of the main axis with the track to be traced;

FIGURE 3 is a block diagram of an apparatus operating according to the new method;

FIGURE 4 shows diagrammatically the tilting of the main axis of the flying spot pattern;

FIGURE 5 shows schematically the obtaining of stereoscopic nuclear track patterns from a bubble chamber by means of two photographic cameras;

FIGURES 6a and 6b are one pair (I and II) of stereoscopic nuclear track patterns;

FIGURE 7 illustrates the scanning motion of the flying spot pattern across the nuclear track patterns I and II;

FIGURE 8 is a block diagram of an apparatus for the evaluation of stereoscopic nuclear bubble chamber photographs which makes use of the new method according to the invention;

FIGURE 9 shows a correlator connected to two photoelectric receivers;

FIGURES l0af are different impulses as obtained from the photoelectric receivers and subsequently amplified and superimposed.

3 DESCRIPTION OF THE PREFERRED EMBODIMENTS The flying spot pattern may be subdivided in four quadrants of equal area. One of the two subdividing lines connects the two points of greatest distance of the Fattern (main axis), the other line extends normal to the first line, crossing the latter in its central point.

By means of the deflecting voltages and currents as are connected to the CRT in any instant the location of the flying spot can be determined by quadrants; and by comparing the signals received from the photoelectric receiver when the flying spot crosses the track, those control signals are obtained which are needed for correcting the location of the flying spot pattern with regard to the track to be traced.

By comparing the quadrant signals I+III with the quadrant signals II+IV, control signals are derived for correcting the elevation of the main axis with its central point serving as the pivot. A comparison of the quadrant signals I+IV with those of the quadrants II+III -results in obtaining control signals for the location of the main axis central point.

In FIGURE 1 is depicted a portion of the track to be traced 1 and the flying spot pattern 2. The latter is produced by a CRT 3 shown in FIGURE 2. Connected to the cathodes 4 of CRT 3 are three pairs of six single deflection voltages. The first pair consists of two A-C voltages of equal amplitude but of phases which difier by 90. The second pair consists of two A-C voltages of balanced phase but different amplitudes; and the third pair consists of DC voltages which change only slowly in comparison to the tracing frequency.

Shape and location of the flying spot pattern is defined by the deflection voltages and currents connected to the CRT as is readily discernible from FIGURE 2. First be it assumed that an AC voltage is connected to each of the deflection systems of the CRT being located normal to each other. Further be it assumed that the A-C voltages are of equal amplitude but differ in their phase by 90. The result will then be a circle as illustrated in the center of FIGURE 2a.

If, however, only A-C voltages are connected to the deflection systems which are balanced in phase but have difierent amplitudes the resulting pattern will be a line the elevation of which depends on the ratio of the amplitudes of said voltages (FIG. 2b).

On the other hand, if only DC-voltages are connected to the deflection systems which do change only slowly, a slowly moving spot of light will appear on the screen of the tube (FIGURE 2c). superimposition of these three kinds of voltages by means of additive amplifiers 14, 15 (FIGURE 2d) and connecting them to the deflection systems will result in the required oblong shape of the flying spot pattern.

Upon coincidence of the flying spot patterns central point with the track to be traced, D-C. voltages are obtained which are proportional to the position of the flying spot pattern on the track to be traced and which represent the xand y-coordinates of the point of coincidence. After correcting the inclination of the pattern parallel to the track, the components of the in-phase-AC-voltages (FIGURE 2b) represent the slope of the track in this point. Proportional D-C voltages g and 1 are integrated and connected to the deflection systems in order to cause the central point of the flying spot pattern to be displaced in the direction of the patterns main axis.

A block diagram of an apparatus by which the new method may be performed is illustrated by way of example in FIGURE 3. Input potentiometers 3'10, 320 are provided in connection with integrators 31, 32 for adjusting the speed of the scanning motion. The outputs of 4 said generators are connected to the inputs of deflection amplifiers '14 (for the x-coordinate) and 15 (for the ycoordinate). Said amplifiers are provided with several additive inputs the function of which being described hereinafter. The outputs of said amplifiers are connected to static deflector plates in the CRT. As is well known to those skilled in the art magnetic deflector coils may be substituted for said static deflector plates. A threshold gate as is well known as a sawtooth generator in oscillographic CRTs closes electronic contacts whenever the light spot reaches the rim or edge of the screen. The light spot moves then back and starts the scanning of a new line. For sake of simplicity in FIGURE 3 said electronic contacts are depicted as mechanical circuit breakers 311, 321 connected in parallel to the integrating capacitors 311, and 321'.

When during the scanning motion the flying spot comes first across a track to be traced, the multiplier 21 sends a pulse which is amplified by the amplifier 22. In a delayed trigger circuit 39 another pulse is generated and kept for some time by the capacitor 139. The rectifier also in the feed back circuit illustrates that the rise of the pulse must not be delayed.

By means of a nand-gate 38 which in this phase of operation does not yet work and an amplifier 40 a number of electronic contacts 41 are controlled. For sake of simplicity in the drawing said contacts 4'1 are again depicted as mechanical circuit breakers and their connections are not shown. Said contacts 41 cause the inputs of the in tegrators 31, 32 to be shunted, which results in the stopping of the light spot in its instant position until additional control signals are received by the other inputs of the additive amplifiers 14, 15. Moreover, said contacts 41 cause the contacts 229, 230 in front of the inputs of the integrators 29, 30 to be closed. The integrators 29, 30 operate in the same manner like the integrators 31, 32. Contrary to those, however, they are fed by the variable input voltages g and 1 These voltages must first be generated in the integrator stages 27, 28. However, said stages are biased by small starting voltages from the supply voltage via high ohmic resistors 27a, 28a.

Via a Wire connection 36 said contacts 41 also interrupt the electron-beam current in a Vidicon 33 on which an optical image of the CRT screen is formed by-means of a beam splitter, not shown.

A-C voltages influence the apparatus in the following manner: In an oscillator OSZ having two counter phase outputs an A-C voltage of the frequency 2 is generated. Preferably, this voltage is rectangularly shaped. Both outputs of said oscillator are connected to the inputs of two flip-flop stages 1 18, the latter one having two outputs. All A-C voltages are conducted to modulators M of known design and having two inputs and one output. If an A-C voltage and a D-C voltage are connected to the inputs of such a modulator, at the same time an A-C voltage is obtained from the output the phase of which is identical or diflers by from the phase of the A-C voltage connected to the input terminal. The inversion of the phase is determined by the inversion of the sign of the D-C voltage. If, however, two A-C voltages having equal frequency are connected to the inputs, a D-C voltage will be obtained from the output. Said D-C voltage will be positive if the two A-C voltages are in phase, and it will be negative if the A-C voltages are counter phased. In this case a modulator may be termed a phase sensitive rectifier.

The arbitrary starting voltages E and -which, however, must not be zero-are conducted to the rnodulators 10, 11, 16, 17, 19 and 20. They are decisive for the phase of the A-C voltages in the outputs of the modulators. While the modulators 10 and 11 are of such a design that the amplitudes .5 and 1 also remain proportional, the modulators 16, 17, 19 and 20 produce constant amplitudes which only change in sign.

By means of the integrators 12, 13 the output signals of the modulators 10, 11 are turned into triangle-shaped voltages a) 7- having proportional amplitudes and are then conducted to the additive amplifiers 14, 15. Since the modulators 10, 11 are controlled by the same voltage from the flip-flop stage If the voltages E and 1;,

are balanced. On the screen of the CRT they will thus produce a small line having components proportional to the voltages E and 1 In the differential stages connected to the integrators 12, 13 the differential quotients and 1; of the triangle-shaped voltages are produced of which the small fraction on is added to the other component, in

one case with reversed sign. This results in the following deflection voltages for the flying spot pattern:

wig which in the same figure means a displacement to the top.

If both triangularly shaped voltages decrease,

will cause a displacement to the lower right. This results in a clockwise rotation of the light spot: the flying spot pattern. As is readily discernible an apparatus comprising the block diagram according to FIGURE 3 will produce the required flying spot pattern through all quadrants and for every angular value.

The modulators 23, 24 of FIGURE 3 are on the one hand supplied with the voltages of the modulators 16, 17, and on the other hand with the pulses of the amplifier 22.

Now, taking into consideration the flying spot pattern as illustrated in FIGURE 1 which is caused by rotation of the light spot with the frequency 1] it will be readily understood that, for example, the quadrants I and III coincide with the positive half-waves of the rectangularly shaped voltage having the frequency 2 while on the other hand the quadrants II and IV coincide with the negative half-wave of said voltage (or vice versa). If the flying spot pattern should now rest in a tilted position on the track to be traced-for example in such a way that the quadrant I is above the track, the quadrant III below the tracksignals will be produced by the photoelectric receiver 21 when the spot rotates through the quadrants II and IV.

For adjustment the flying spot pattern must be tilted in a clockwise direction, i.e. the value .5 must be increased, the value 1 however, must be decreased. Control signals are now generated by the modulators 10, 23 and 17, 24 respectively, and as a result a positive signal d5 will be received by integrator 27 which signal serves to increase its output voltage 5 Integrator 28, however, receives a negative signal d1; whereby the voltage 1; is reduced.

If the four quadrants I through IV cross the track to be traced evenly the signals di and da will be zero, which results in the voltage 5 and 1 remaining unchanged: the main axis of the flying spot pattern is in a. tangential position relative to the track to be traced.

The integrator 29, 30 now move the flying spot pattern in the direction of its main axis by producing the values x-fdt and y-f dt. If the track to be traced changes its direction new control signals ds and d1; will be generated thereby keeping the central point of the main axis continuously in tangential relationship with the track to be traced.

The modulators 19, 25, and 20, 26 also eflect that parallel displacement of the main axis from the flying spot pattern are corrected until again the quadrants I+IV and II +III cross the track evenly, which results in the photoelectric receiver 21 generating equal pulses.

As will be readily understood to this end the signals from the photoelectric receiver must be multiplied by a signal having the frequency 1 The signals resulting from this multiplication are fed to the integrators 29, 30 until they have become zero by the corrections which take place. The main axis will then be exactly the tangent to the track to be traced with its central point being positioned on the track.

After termination of the tracing the capacitors of the integrators 29, 30 must be shunted by means of electronic contacts, not shown. The flying spot will then move back to the beginning of the line because the capacitors of the integrators 31, 32 are still charged. By switching off the trigger 39, all contacts 41 will resume their starting position.

The scanning motion of the flying spot is then continued with the beam current of Vidicon 33 switched on via wire 36. Since the screen of the CRT is imaged on the Vidicon by way of a beam splitter (not shown) the traced track has caused on the Vidicon 33 2. corresponding image of charges. If, now, the flying spot crosses a track already previously traced, trigger 39 will respond. Simultaneously, however, Vidicon 33 will send a pulse via wire 37. Both signals counterbalance each other in the NAND-gate 38. The scanning motion thus is not stopped; it is rather continued until a track is found which has not yet been traced. Only then the pre-described tracing performance starts again.

It will now, by way of example, be explained in what manner the new method of tracing a track is made use of in a new method and apparatus for tracing nuclear tracks on stereoscopic bubble chamber track photographs. This method roughly comprises the steps of Scanning a first stereoscopic track photograph for a track to be traced by means of a flying spot;

Simultaneously scanning a second stereoscopic track photograph by means of a second flying spot in the direction of one coordinate which is derived from the coordinates of the first photograph according to the geometric configuration of both stereoscopic photographs;

Stopping the scanning motion of the first flying spot when said first flying spot crosses a track;

Shifting the scanning motion of the second flying spot to the other coordinate-again according to the geometrical configuration of both stereoscopic photographswhile producing on both photographs flying spot pattern adjusted according to the direction of the track in the first photograph;

Stopping the scanning motion of the flying spot pattern on the second photograph when the flying spot first crosses a track;

Adjusting the position of the flying spot pattern on the second photograph according to the direction of the crossed track while maintaining the synchronous oscillation of the both flying spots;

Resuming the scanning motion of the second flying spot in the second coordinate on the second photograph if noncorrelation between the tracks on the first and second photographs is determined;

Or proceeding with tracing both tracks according to the hereinbefore described method if correlation between tracks is established.

It is the main advantage of this method of tracing nuclear tracks on stereoscopic bubble chamber track photographs that after the scanning period identical tracks are traced synchronously on both photographs by means of separate tracing devices and by making use of the statistic character of the track structure. A correlator is employed, the output signals of which are utilized for adjusting the tracing synchrony. Events along the tracks are registered and evaluated only if they are sensed by both devices simultaneously.

In FIGURE is schematically outlined the technique by which the two stereoscopic photographs I and II are obtained and also what geometrical relation of the spots on said photographs exists. In the bubble chamber 510' indicated in dotted lines there is, for example, the point P of which an image is formed on the photographs I and II by means of the photographic cameras 511 and 512. The direct line from P to camera 511 is marked 513, the image point on photograph I is referred to as 514. In like manner the direct line from P to camera 512 is marked 515, and the image point on photograph 11 is marked 516. As can be seen from the figure all points on line 513 correspond to the same image point 514 on photograph 1. However, on photograph II these same points form a line the location of which is defined linearly by the location of image point 514 on photograph 11.

In FIGURE 7 two photographs I and II are schematically illustrated with tracks to be traced 717 and 718, both being images of the same bubble track. As indicated the flying spot performs for some time a scanning motion on photograph I along the lines 719. Said scanning motion is continued until the flying spot first crosses track 717. During this scanning motion the flying spot on photograph 11 moves synchronously to the first mentioned flying spot on photograph I, however, said second flying spot moves repeatedly along the same line 719'. Control means are employed adapted to maintain the relative position of both flying spots according to the stereometrical and geometrical configuration of FIGURE 5. Upon crossing the track to be traced by the first flying spot on photograph I the scanning motion on photograph I is stopped. On photograph II the scanning motion is now shifted to the second coordinate in such a manner as to scan photograph II from bottom to the top along line 721, the direction of said line resulting from the stereogeometrical configuration. In addition, both flying spots are caused to oscillate along a pattern of oblong shape as described hereinbefore, the position of said pattern being determined by the direction of track 717 on photograph I.

If now the flying spot pattern on photograph II, while moving along line 721, first crosses a track, the motion along line 721 is stopped, and by means of a correlator to be described hereinafter it is evaluated whether the crossed track is track 718 or some other track. To this end, first the position of the flying spot pattern must be adjusted to the direction of the crossed track, however, without interrupting the synchrony of the oscillation of both flying spots. If the crossed track is not track 718 but some other track, the correlator will not send a D-C signal. This causes the scanning motion to be resumed again along line 721. Does, however, the flying spot pattern cross track 718 the correlator will send a D-C signal which starts the joint tracing of the tracks 717 and 718. During said tracing the correlator will continuously send control signals which serve to increase or decrease the tracing speed along track 718 in order to ensure that on both photographs constantly the same bubbles are traced simultaneously.

Should the accuracy of the scanning motion along line 718 on photograph 11 be not absolutely correct with regard to the direction of track 717 and the stereogeometrical configuration on the one hand, and the statistical structure of the bubble configuration on the other hand, it may then happen that the correlator sends no D-C signal even if the correct track is crossed on photograph II because not the identical bubblesor rather their imagesare crossed on photograph I and II. It is, therefore advisable to have the flying spot pattern on photograph II trace each crossed track in both directions a short distance in order to ensure that upon crossing the correct track a D-C signal will positively be sent.

It is within the scope of the invention to compensate for any possible perspective shortenings of the tracks in the same manner as outlined above by providing additional modulators controlling the amplitude of the second flying spot pattern voltage.

All events of interest on the tracks are of geometrical nature. They are constituted, for example, by branches, breaks or the end of the track. The new method measures these events in analogous manner: curvatures, for example, by means of the second differential quotient. Upon exceeding a predetermined value triggers are actuated which stop the tracing proceedings and thereby establish the coordinates (=deflection voltages) of the place of the event. Said coordinates are then digitized and stored. It is of particular importance that an event is registered only if both triggers attached to the photographs I and II respectively are actuated simultaneously. Thereby it is ensured that crossings of tracks are not, by mistake, taken for events.

In FIGURE 8 an apparatus for performing the method is illustrated schematically. The light beam of a CRT 101 produces on the photograph I a light spot after having passed through a beam splitter 102 and a lens 103. An image of said light spot is formed by lens 104 on the photoelectric receiver 105. A Vidicon 107 is provided on the screen of which also an image of said light spot is formed via the beam splitters 102, 108 in such a way as to bring about coincidence of the impinging beam with the cathode ray of the Vidicon on the screen of the latter. Additionally a further beam splitter 111 and a reflecting mirror 114 are disposed by means of which the light beams of the CRT 101 are directed to two gratings 110, 113. The lines of said gratings extend in directions normal to each other. Photoelectric receivers 109 and 112 are located behind said gratings 110, 113. The outputs of said photoelectric receivers being connected to control stages 115, 116 which in turn are connected to counter mechanisms 117 (for the x-coordinate) and 118 (for the y-coordinate).

-All the elements required for tracing a track according to the new method and being illustrated in FIGURE 3 of this application are contained in and schematically represented by block 106. The latter being connected by Wires 1061:, 10% to the aforementioned elements.

A like device is provided for photograph II, the elements having the reference symbols 201 through 218.

To the photoelectric receivers 105, 205 a correlator 120 is connected, the details of which are illustrated in FIG- URE 9. Further, a stage 121 is employed comprising the control elements for adjusting the coordinates in both photographs I and II as well as elements for programming the additional scanning motions. These elements are roughly the same as those contained in the blocks 106, 206. They send signals which are directed to the circuits 106, .206 and which effect the required corrections.

The correlator 120 comprises an additive amplifier and a differential amplifier 151 (FIGURE 9), the inputs of which are connected in parallel to the photoelectric receivers 105, 205. The output of amplifier 150 is connected to a differential stage 152, the output signals of said stage being supplied to trigger stage 153. The output signals of amplifier 151 are conducted to a modulator 154 together with the output signals of trigger stage 153. Said modulator 154 is in turn connected to a further modulator 155, the latter being supplied by a rectangular voltage having the frequency 1 the same frequency with which the flying spot oscillates.

The above described device operates in the following manner: The light beam generated by CRT 101 produces a spot of light on photograph I. During the scanning motion this light spot causes no image of charges on the screen of the Vidicon 107, this being prevented by the synchronously oscillating cathode ray of this Vidicon. During the tracing of the track, however, the cathode ray current is switched off, which results in an image of charges being produced on the Vidicon screen, the location and shape of said image corresponding identically to the traced track on photograph I. As already mentioned above, this image of charges prevents a second tracing of an already traced track it the scanning motion is resumed later.

Scanning of the gratings 110, 113 serves to determine the exact coordinates of tracks and events. During the scanning proceedings of the photographs for selecting a track to be traced and the first tracing of said track the photoelectric receivers 109, 112 are switched off, since the light spot of CRT 101 is too bright and expanded for the grating structure to be resolved. During this phase of operation, the Vidicon is switched on. Thereafter the track is traced again, this time by means of a smaller and more slowly oscillating light beam. During this second tracing, the photoelectric receivers 109, 112 are switched onzhowever, the Vidicon is not used.

Besides by the counter pulses the control stages 115, 116 and 215, 216 are additionally controlled by the xand y-deflection voltages of the CRT 101, which voltages are differentiated. The resulting signals are fed to trigger stages, said stages supplying said counter impulses to the additive counter input if the deflection voltage increases, and to the subtracting counter input if the deflection voltage decreases. Thus, always the instant coordinate of the flying spot is counted which is close by the track. Establishing of the mean value for one oscillation can be achieved, for example, by several time controlled callings of coordinates.

If the device as a whole operates more slowly, it is, of course, possible to substitute a mechanically pivotable mirror for the beam splitter 108 thereby achieving a better utilization of the light.

Producing the signals in the correlator 120 is performed as follows:

As shown in FIGURES a, 10b wherein the axes of abscissae represent synchronous periods of time both photoelectric receivers 105 and 205 generate, for example, pulses I I These signals are either added up in amplifier 150 (FIGURE 100) or subtracted in amplifier 151 (FIGURE 10d). After differentiation of the sum signals-by stage 152 the signals will be of the shape depicted in FIGURE 9e. By modulation by means of modulator 154 a signal will be obtained of the shape illustrated in FIGURE 9 This signal being of the following nature:

If pulse 1 is generated somewhat later than pulse I but does still overlap pulse I a negative final signal will result. If, however, pulse I is generated ahead of pulse 1, and also still overlaps pulse 1 a positive final signal will result. If pulses I and I coincide, the difference of said signals as well as the final signal will be zero. 'If the pulses I and I are generated at different times, so as not to overlap each other the final signal will also not contain a D-C current component, the difference, however, still having strong pulses.

From this it can be comprehended that if all pulses I are generated equally prior to or later than pulses I always the same positive or negative final correction signal Willbe produced and a strong D-C signal will be added up: i.e. correlation exists.

Sincethe flying spot constantly changes its direction of movement while oscillating along its pattern, pulses in the order I I are obtained in the One direction (=positive signal) and in the order I I in the other direction thereby generating a negative correction signal, this change of signs is corrected by the modulator 155.

What I claim is:

1. A method of tracing a track by means of the flying spot of a cathode ray tube comprising the steps of generating an oblong pattern by a rotating flying spot;

tilting the flying spot pattern in order to adjust the main axis to a direction parallel to the tangent to the track to be traced;

shifting the flying spot pattern in order to bring the central point of said main axis into contact with said track to be traced, and

displacing the flying spot pattern in the direction of its main axis.

2. A method of tracing a track by means of the flying spot of a cathode ray tube comprising the steps of;

generating an oblong flying spot pattern by connecting at least six deflection voltages in pair of two to the cathode ray tube, said flying spot pattern being of approximately double the width and more than ten times the length of the Width of the track to be traced;

producing a scanning motion of said flying spot pattern;

generating in a photoelectric receiver output signals whenever the light spot crosses the track to be traced; stopping said scanning motion upon crossing the track to be traced;

com aring the signals related to the four quadrants of the flying spot pattern by means of double frequency and single frequency phase sensitive rectifiers and integrators and obtaining correction signals for the elevation of the main axis and the central point of the flying spot pattern adjusting said main axis and said central point of said flying spot pattern by means of said correction signals in tangential relationship to the track to be traced;

integrating D-C signals proportional to the A-C components of the pattern voltage for the displacement of said flying spot pattern in the direction of its main axis;

obtaining from said control signals information relative to the location and/or the shape. of the track to be traced.

3. A method of tracing a track according to claim 2 and further comprising the steps of recording the traced track by means of a storing television camera tube;

resuming the scanning motion after the termination of the tracing performance from the point where the flying spot pattern first crossed the track;

preventing the stopping of the scanning motion if the flying spot pattern again crosses a track already traced by using the video pulse of said television camera tube.

4. A method of tracing a track on a pair of stereoscopic nuclear bubble track photographs by means of the flying spot of a cathode ray tube comprising the steps of scanning a first stereoscopic track photograph for a track to be traced by means of a flying spot;

simultaneously scanning a second stereoscopic track photograph by means of a second flying spot in the direction of one coordinate which is derived from the coordinate of the first photograph according to the geometric configuration of both stereoscopic photographs;

stopping the scanning motion of the first flying spot when said first flying spot crosses a track;

shifting the scanning motion of the second flying spot to the other coordinateagain according to the geometrical configuration of both stereoscopic photographswhile producing on both photographs flying spot patterns adjusted according to the direction of the track in the first photograph;

stopping the scanning motion of the flying spot pattern on the second photograph when the flying spot first crosses a track;

adjusting the position of the flying spot pattern on the second photograph according to the direction of the crossed track while maintaining the synchronous oscillation of the both flying spots;

resuming the scanning motion of the second flying spot in the second coordinate on the second photograph if non-correlation between the tracks on the first and second photographs is determined;

or proceeding with tracing the tracks if correlation between tracks is established.

5. A method of tracing a track according to claim 4 and further comprising the steps of tracing the tracks having events after termination of the first tracing performance with light spots of smaller expansion and slower oscillation speed;

simultaneously projecting the flying spots on gratings having lines extending normally to each other and having one photoelectric receiver each disposed behind said gratings in the direction of the impinging light;

alternately supplying the generated counter pulses to the additive and the subtractive counter inputs by means of triggers, said triggers being controlled by the total deflection voltages after said voltages have passed through differential stages.

6. Apparatus for tracing a track by means of the flying spot of a cathode ray tube, said apparatus comprising a cathode ray tube (CRT) adapted to generate a flying spot;

a first deflection amplifier (14) for deflecting said flying spot in the direction of the x-coordinate;

a second deflection amplifier (15) adapted to deflect said flying spot in the direction of the y-coordinate;

first integrator stages (31, 32) adapted to produce a scanning motion of said flying spot pattern, the outputs of said integrators being connected to the inputs of said deflection amplifiers;

a photoelectric multiplier (21) adapted to generate pulses upon crossing the track by said flying spot pattern;

an oscillator (OSZ) adapted to generate an AC voltage of the frequency 2 two flip-flop stages (2 18) connected to said oscillator;

modulators (10, 11, 16, 17, 19, 20) determining the phase of the output A-C voltages;

second integrator stages (12, 13) connected to said modulators (10, 11) and transforming the output signals of said modulators into triangularly shaped A-C voltages;

differential stages (42, 43) connected to said integrators adapted to produce the differential quotients of said triangularly shaped A-C voltages an amplifier (22) adapted to amplify the pulses generated by said photoelectric multiplier (21);

modulators (23, 24) being supplied with the switching voltages of modulators (16, 17) of frequency of 2 and with the pulses sent by amplifier (22);

third integrator stages (27, 28) adapted to generate control signals for tilting the main axis of the flying spot pattern, and

fourth integrator stages (29, 30) connected to said second integrator stages and being adapted to generate signals for the displacement of the flying spot pattern in the direction of its main axis.

7. Apparatus for tracing a track by means of the flying spot of a cathode ray tube according to claim 6 and further comprising a storing television camera tube (33);

means adapted to project an image of the flying spot pattern on the screen of said storing television camera tube, thereby forming a charge image on said screen;

a delayed trigger (39) connected to said amplifier (22);

a nand-gate (38) connected to said storing television camera tube and to said trigger (39);

an amplifier (40) connected to the output of said nandgate (38) and electronic switching means connected to said amplifier,

said switching means being adapted to shunt said first integrator stages (31, 32).

8-. Apparatus for tracing a track on a pair of stereoscopic nuclear bubble track photographs comprising two cathode ray tubes (101, 201) adapted to project a spot of light each on one of the photographs (I, II);

two photoelectric receivers (105, 205) adapted to generate electric pulses;

two storing television camera tubes 107, 207);

means (108, 208) adapted to project an image of said flying spot onto the screen of the storing television camera tube;

two pairs of gratings (110, 113 and 210, 213), in each pair, the lines of one grating extending normally to the lines of the other grating;

means (111, 114, 211, 214) adapted to project an image of said flying spot onto said gratings;

one photoelectric receiver (109, 112, 209, 212) disposed behind each of said gratings in the direction of the impinging light;

control stages (115, 116, 215, 216) connected to said photoelectric receivers;

counter mechanisms (117, 118, 217, 218) connected to said control stages;

devices for tracing a track (106, 206) connected to said first photoelectric receivers (L105, 205) comprising;

a cathode ray tube spot;

a first deflection amplifier (14) for deflecting said flying spot in the direction of the x-coordinate;

a second deflection amplifier (15) adapted to deflect said flying spot in the direction of the y-coordinate;

first integrator stages (31, '32) adapted to produce a scanning motion of said flying spot pattern, the outputs of said integrators being connected to the inputs of said deflection amplifiers;

a photoelectric multiplier (21) adapted to generate pulses upon crossing the track by said flying spot pattern;

an oscillator (OSZ) adapted to generate an AC voltage of the frequency 21;

two flip-flop stages (11, 18) connected to said oscillator;

modulators (10, 11, 16, 17, 19, 20 determining the phase of the output A-C voltages;

second integrator stages (12, 13) connected to said modulators (10, 11) and transforming the output signals of said modulators into triangularly shaped A-C voltages;

differential stages (42, 43) connected to said integrators adapted to produce the diflerential quotients of said triangularly shaped A-C voltages an amplifier (22) adapted to amplify the pulses generated by said photoelectric multiplier (21);

modulators (23-, 24) being supplied With the switching voltages of modulators (16, 17 of frequency of 2f and with the pulses sent by amplifier (22);

third integrator stages (27, 28) adapted to generate control signals for tilting the main axis of the flying spot pattern;

fourth integrator stages (29, 30) connected to said second integrator stages and being adapted to generate signals for the displacement of the flying spot pattern in the direction of its main axis;

a storing television camera tube (33);

means adapted to project an image of the flying spot pattern on the screen of said storing television camera tube, thereby forming a charge image on said screen;

a delayed trigger (39) connected to said amplifier (22);

a NAND-gate (38) connected to said storing television camera tube and to said trigger (39);

an amplifier (40) connected to the output of said NAND-gate (38);

(CRT) adapted to generate a flying electronic switching means connected to said amplifier, said switching means being adapted to shunt said first integrator stages (31, 32); and

a correlator stage (120) connected to said first photoelectric receivers (105, 205) and being adapted to establish whether two tracks which are crossed by the flying spots on photographs I and II respectively are identical;

a control stage (121) being adapted to adjust the coordinates of the scanning motion on both photographs I and II according to the stereogeometrical configuration of the track to be traced on said both photographs.

9. Apparatus for tracing a track according to claim 8,

the correlator (120) therein comprising an additive amplifier (150) and a differential amplifier (151), the inputs of which are connected in parallel to the photoelectric receivers (105, 205),

a differential stage (152) connected to the amplifier a trigger (153) connected to said differential stage a modulator (154) being supplied with the output signal 14 of the amplifier (151) and the output signal of the trigger (153) and a modulator (155) connected to said modulator (154) receiving a rectangularly shaped voltage of the frequency 1f.

10. Apparatus for tracing a track according to claim 8 in which said means for projecting an image of said flying spots onto the screen of said storing camera tube comprises stationary beam splitters.

11. Apparatus for tracing a track according to claim 8, in which said means for projecting an image of said flying spot onto the screen of said storing camera tube comprises pivotably mounted mirrors.

References Cited UNITED STATES PATENTS 2,974,254 3/1961 Fitzmaurice et al. 315-10 3,350,505 10/1967 Bakis 315-10 RODNEY D. BENNETT, IR., Primary Examiner.

J. P. MORRIS, Assistant Examiner.

US. Cl. X.R. 178-618 

